That's only half the problem. Overlooked in the conversation is a particular group of boomers: doctors and nurses who are itching to call it quits. Health-care economists and other experts say retirements in that group over the next 10 to 15 years will greatly weaken the health-care workforce and leave many Americans who are newly insured under the new legislation without much hope of finding a doctor or nurse.

Nearly 40 percent of doctors are 55 or older, according to the Center for Workforce Studies of the Association of American Medical Colleges. Included in that group are doctors whose specialties will be the pillars of providing care in 2014, when the overhaul kicks in; family medicine and general practitioners (37 percent); general surgeons (42 percent); pediatrics (33 percent), and internal medicine and pediatrics (35 percent).

About a third of the much larger nursing workforce is 50 or older, and about 55 percent expressed an intention to retire in the next 10 years, according to a Nursing Management Aging Workforce Survey by the Bernard Hodes Group. New registered nurses are flowing from colleges, but not enough to replace the number planning to leave the profession.

"Moving into the future, we see a very large shortage of nurses, about 300,000," said Peter Buerhaus, a nurse and health-care economist and a professor at Vanderbilt University. "That number does not account for the demand created by reform. That's a knockout number. It knocks the system down. It stops it."

According to the census, baby boomers include the 66 million Americans born between 1946 and 1964.

In an article for the Journal of the American Medical Association, Buerhaus and colleagues Douglas Staiger and David Auerbach predicted that there will be at least 100,000 fewer doctors in the workplace than the 1.1 million the federal government projects will be needed in 2020 under the health-care overhaul.

The authors analyzed the American Medical Association Masterfile survey of the nation's physicians and found that it overestimated the number of active older physicians who are baby boomers.

Using the monthly Current Population Survey of the census bureau, the writers found that older doctors aren't nearly as active as those who are 54 and younger, and that their lack of activity must be taken into account when determining the available level of care after the overhaul has been implemented.

"There's a much more rapid retirement of physicians," Buerhaus said. "What does this retirement mean? This will mean at least 100,000 fewer doctors in the workplace in 2020."

He said the article does not estimate the change in demand or the level of recruitment by medical colleges, which is being beefed up significantly under the health-care law.

Lori Heim, president of the American Association of Family Practitioners, said someone might soon have to replace her. "My age group is looking at when we are going to retire," said Heim, who is 54. "More physicians are changing their practice, doing things that have less calls. They want administrative roles."

Heim said her statement is based on an impression. "I haven't seen any numbers on this." But, she said, her association is among the many that for years have pointed out the shortage of primary care doctors and nurses to the White House and Congress.

Although the association supported the health-care overhaul, it thinks the law does not go far enough to address the workforce shortages projected for the coming decade.

Reform will add demand on top of shortages already projected, and as a result the health-care workforce might not be attractive.

According to the American Association of Colleges of Nursing, 75 percent of nurses said in a survey they think the shortage "presents a major problem for the quality of their work life, the quality of patient care, and the amount of time that nurses can spend with patients."

In a survey by New York University's Christine Kovner, 13 percent of newly registered nurses changed principal jobs after a year, and 37 percent said they were ready to change jobs. A separate report found that the turnover rate for registered nurses was 13 percent. A University of Pennsylvania study called for 30,000 extra nurses per year to be graduated to meet health-care needs.

"I think the big story is . . . the future of nursing is dominated by aging baby-boomer nurses who are going to retire, and we are looking at massive shortages," Buerhaus said. "Others are not picking up the retirements of physicians. There's just not going to be as many doctors as needed out there."